Efforts to investigate the ionic mechanisms of excitation in smooth muscle and cardiac muscle through voltage-clamp techniques have yielded controversial results. The equivocal nature of these data in terms of quantitative statements on the magnitude, kinetics and even components of ionic currents has limited the useful application of this technology in the study of mechanisms of action on drugs and hormones. My long term interests in smooth muscle concerns the mechanisms of hormonal control of reproductive smooth muscle activity. The present proposal is designed to evaluate and eliminate the compromising effects of tissue geometry by exploiting the simple geometry characteristics of the mesotubarium. Small strands consisting of a few cells in cross section will be studied in the voltage-clamp system. Furthermore, the fact that this smooth muscle system responds to sex hormones provides the opportunity to begin analysis of hormonal mechanisms uncompromised by the effects of complex tissue geometry.